I found that the Dewalt 28v tools take 8 26650 batteries and got some from Amazon.

Then welded them together exactly as the ones that came out of the battery pack, checked with a voltmeter and 28v.

Then I pulled the control board from the old battery and went to connect it to the battery, immediately had what appears to be a short circuit with blue smoke coming from the sealed board.
This maybe what killed the original battery, I’m not sure, but it’s obviously not workable.

Any ideas on how to replace that board from the 28v battery since dewalt doesn’t support them any more?

I have another battery, but I’m almost afraid to see if it works, since I’d rather not burn up another one.

I did get one of the battery packs to work, I think either I had wired one of the cells incorrectly or the control board was already fried.

I used the other control board and rewelded the pack while very carefully following the old one, and popped it on the charger.

The charger seemed to think it was full within a few of seconds, tried it on the saw, and it fired right up for about 4-5 seconds then slowly powered down like batteries dying, keyed the switch again and the same thing.

It kept repeating this cycle over and over.

So apparently the cells need to be some specific high discharge cells and the ones I bought on amazon don’t fit the bill.

So if anybody has a source for more of the 26650 batteries that will discharge fast enough to run the saw, and a place to get the boards, to rebuild the batteries, I’d like to hear it.